There was a lower level loop, intended for commuter trains, but it was abandoned after it filled up with smoke because the New Haven had not electrified its commuter operations. Most of it is destroyed after the reconstruction recently, and there's no way to use it for expanded capacity.

As Mr. Ege notes, the remnants of the lower level loop at South Station disappeared during the major reconstruction of the building in the 1980s. It was never used in regular service because of the smoke problem and the fact that the planned electrification of the New Haven's Boston commuter service never happened. The loop level space beneath South Station's waiting room was used for years as bowling alley, into the late 1960s at least, but the bowling alley had closed long before the rebuilding. The eastern portal of the tunnel that led to the loop lasted until the Big Dig construction; it was out near the Fort Point Channel bridge between the Shore Line and Old Colony tracks. The other portal had disappeared when the trackage that served the station's original baggage wing along Atlantic Avenue was removed about fifty years ago.

cytotoxictcell wrote:HA
I know this topic is old, but how did the new haven railroad turn the locomotives around? like when they arrived at South Station how did they turn the locomotive around to head back south?

As far as I know, the New Haven had a balloon track in the vicinity of South Station with which to turn their locomotives.

cytotoxictcell wrote:HA
I know this topic is old, but how did the new haven railroad turn the locomotives around? like when they arrived at South Station how did they turn the locomotive around to head back south?

As far as I know, the New Haven had a balloon track in the vicinity of South Station with which to turn their locomotives.

It was really shortsighted to eliminate the underground loop in years past, given that the NEC is now electrified and could have used it, as could an electrified Fairmount line. When the postal building is torn down, maybe the loop can be restored, although the building at the corner of Dorchester Ave and Summer Street would probably also have to be torn down (no big loss there!)

"The penny candy store beyond the El
is where i first fell in love
with unreality.....
Outside the leaves were falling as they died.
A wind had blown away the sun."
----Lawrence Ferlinghetti

By the time the approach tunnel on the B&A side of the station was removed circa 1960, it hadn't been used in about 60 years. Passenger service was a diminishing thing and at the time there was no prospect of either a revival or electrification, so no reasonable person would have foreseen a future use. When the remnants of the loop were removed in the mid-1980s, there wasn't enough of it left to even think of saving during the South Station reconstruction.

When the postal building is torn down, maybe the loop can be restored, although the building at the corner of Dorchester Ave and Summer Street would probably also have to be torn down (no big loss there!)

You'd also have to remove the very large I-90 tunnel that now occupies the space beneath the South Station approach tracks where the loop used to be. Some people might object to that.

To add to all the other reasons the loop never would have been NEC-compatible are two more:
There is the lack of headroom. Except for the original AC, NH electrification was 3rd-rail or overhead 600v-DC. A look at the photo shows that while there was adequate clearance for trolley-voltage service, high-voltage catenary could not have been installed there because of flash-over.
The plans show tight-radius curves that would disallow high-level platforms, and, in all likelihood cause flange- and rail-wear problems, for Acelas and Amfleet equipment.

"Watching trains is better than smoking meth."
--Source, location, and time undisclosed.